From 561b075a252619521888dcd120f1c21716b41913 Mon Sep 17 00:00:00 2001
From: i-just <iwona@pixelandtonic.com>
Date: Thu, 12 Mar 2026 14:54:18 +0100
Subject: [PATCH 1/3] cke compliant language codes

---
 src/Field.php                               |   3 +-
 src/web/assets/BaseCkeditorPackageAsset.php | 107 ++++++++++++++++++++
 2 files changed, 109 insertions(+), 1 deletion(-)

diff --git a/src/Field.php b/src/Field.php
index a059ed52..c94c40b7 100644
--- a/src/Field.php
+++ b/src/Field.php
@@ -1432,7 +1432,8 @@ private function _inputHtml(mixed $value, ?ElementInterface $element, bool $stat
 
         // Add the translation import
         $uiLanguage = BaseCkeditorPackageAsset::uiLanguage();
-        $uiTranslationImport = "import coreTranslations from 'ckeditor5/translations/$uiLanguage.js';";
+        $importCompliantUiLanguage = BaseCkeditorPackageAsset::getImportCompliantLanguage(BaseCkeditorPackageAsset::uiLanguage());
+        $uiTranslationImport = "import coreTranslations from 'ckeditor5/translations/$importCompliantUiLanguage.js';";
 
         $view->registerScriptWithVars(fn($baseConfigJs, $toolbarJs, $languageJs, $showWordCountJs, $wordLimitJs, $characterLimitJs, $imageMode) => <<<JS
 $imports
diff --git a/src/web/assets/BaseCkeditorPackageAsset.php b/src/web/assets/BaseCkeditorPackageAsset.php
index f6f50c8a..32f8c0aa 100644
--- a/src/web/assets/BaseCkeditorPackageAsset.php
+++ b/src/web/assets/BaseCkeditorPackageAsset.php
@@ -23,6 +23,113 @@
  */
 abstract class BaseCkeditorPackageAsset extends AssetBundle
 {
+    // a list of languages supported by CKEditor
+    private static array $ckeSupportedLanguages = [
+        'af',
+        'ar',
+        'ast',
+        'az',
+        'be',
+        'bg',
+        'bn',
+        'bs',
+        'ca',
+        'cs',
+        'da',
+        'de',
+        'de-ch',
+        'el',
+        'en',
+        'en-au',
+        'en-gb',
+        'eo',
+        'es',
+        'es-co',
+        'et',
+        'eu',
+        'fa',
+        'fi',
+        'fr',
+        'gl',
+        'gu',
+        'he',
+        'hi',
+        'hr',
+        'hu',
+        'hy',
+        'id',
+        'it',
+        'ja',
+        'jv',
+        'kk',
+        'km',
+        'kn',
+        'ko',
+        'ku',
+        'lt',
+        'lv',
+        'ms',
+        'nb',
+        'ne',
+        'nl',
+        'no',
+        'oc',
+        'pl',
+        'pt',
+        'pt-br',
+        'ro',
+        'ru',
+        'si',
+        'sk',
+        'sl',
+        'sq',
+        'sr',
+        'sr-latn',
+        'sv',
+        'th',
+        'ti',
+        'tk',
+        'tr',
+        'tt',
+        'ug',
+        'uk',
+        'ur',
+        'uz',
+        'vi',
+        'zh',
+        'zh-cn',
+    ];
+
+    /**
+     * Returns import compliant language code.
+     *
+     * CKEditor doesn't support all the languages that Craft does.
+     * It also often only support the major version, not localized ones (e.g. they support fr but not fr-FR, fr-CA, fr-BE etc).
+     * Since we're now using imports to get the correct translation files, we need to know if the file exists before we import it,
+     * or the field won't render.
+     *
+     * @param string $language
+     * @return string
+     */
+    public static function getImportCompliantLanguage(string $language): string
+    {
+        // first check if we have an exact match
+        if (in_array($language, self::$ckeSupportedLanguages, true)) {
+            return $language;
+        }
+
+        // if not - check if there's a major version that we can use
+        if (str_contains($language, '-')) {
+            $language = substr($language, 0, strpos($language, '-'));
+            if (in_array($language, self::$ckeSupportedLanguages, true)) {
+                return $language;
+            }
+        }
+
+        // if not, default to plain English
+        return 'en';
+    }
+
     /**
      * Returns the CKEditor UI language that should be used based on the app language.
      *

From d1e413222777199a21fa72dba49e01756dc6b7ec Mon Sep 17 00:00:00 2001
From: brandonkelly <brandon@pixelandtonic.com>
Date: Thu, 12 Mar 2026 09:29:34 -0700
Subject: [PATCH 2/3] `@since`

---
 src/web/assets/BaseCkeditorPackageAsset.php | 1 +
 1 file changed, 1 insertion(+)

diff --git a/src/web/assets/BaseCkeditorPackageAsset.php b/src/web/assets/BaseCkeditorPackageAsset.php
index 32f8c0aa..a8c46b46 100644
--- a/src/web/assets/BaseCkeditorPackageAsset.php
+++ b/src/web/assets/BaseCkeditorPackageAsset.php
@@ -110,6 +110,7 @@ abstract class BaseCkeditorPackageAsset extends AssetBundle
      *
      * @param string $language
      * @return string
+     * @since 5.2.0
      */
     public static function getImportCompliantLanguage(string $language): string
     {

From 5ebefb8476d95fe2bb34c7659b6f1f68eed7d4ec Mon Sep 17 00:00:00 2001
From: brandonkelly <brandon@pixelandtonic.com>
Date: Thu, 12 Mar 2026 09:29:45 -0700
Subject: [PATCH 3/3] Release notes

[ci skip]
---
 CHANGELOG.md | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/CHANGELOG.md b/CHANGELOG.md
index 4d6c757f..96ce238c 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -2,9 +2,11 @@
 
 ## Unreleased
 
+- Added `craft\ckeditor\web\assets\BaseCkeditorPackageAsset::getImportCompliantLanguage()`.
 - Fixed a bug where custom `toolbar` config settings were getting ignored. ([#522](https://github.com/craftcms/ckeditor/issues/522))
 - Fixed a bug where files uploaded to Assets fields could also be added to nearby CKEditor fields. ([#523](https://github.com/craftcms/ckeditor/issues/523))
 - Fixed an error that could occur when registering a custom CKEditor plugin. ([#525](https://github.com/craftcms/ckeditor/issues/525))
+- Fixed a JavaScript error that occurred if the control panel was being translated into a language that CKEditor doesn’t support. ([#526](https://github.com/craftcms/ckeditor/issues/526))
 
 ## 5.1.0 - 2026-03-05